Doc Ai, for the games I have created so far, I haven't needed to create characters, per se. But, I have created some random objects, textures, and fancy text which I am proud of. Here's one graphic from my recent Windows 8 app, Coinqueror. Each part is on a separate layer, so six layers total.
Thus, my coin bomb:
<img src="http://simplyadvanced.net/dev/paintdotnet/examples/coin-bomb_1000x1000.png" border="0">
ps - And, for other people who want to see more things possible with Paint.NET, they have a page dedicated to show off works.